Klystrons are commonly employed as a basic signal source in microwave (e.g. satellite link) communication systems. As such, they are required to exhibit a prescribed output characteristic or amplitude response (e.g. flatness) over an operating bandwidth centered about a selected center frequency. Unfortunately, the tuning mechanism through which operation of the klystron is controlled is an extremely sensitive mechanism that does not offer the repeatability desired of signal control devices. Specifically, a klystron cavity tuner typically consists of a plurality of copper cavities and associated tuning slugs which are displaced back and forth in their respected cavities to establish the operational characteristics of the klystron. Usually, each slug is wrapped with a tungsten wire to assure a tight fit in its cavity. As tungsten is a considerably harder metal than copper, repeated movement of the tuning slug will wear down the wall of the cavity, thereby changing its dimensional tolerances and, consequently, its intended operational characteristics.
Because of the mutual interdependence of the tuning of the respective cavities, a klystron cannot be tuned by simply adjusting each tuning slug in an arbitrary order to a preestablished setting. Instead, control of the amplitude response of a klystron must be carried out by repeated back and forth adjustment of each tuning slug, through the use of a respective vernier (micrometer) adjustment knob for each slug, the rotational setting of which is graduated according to a prescribed tuning (number) chart. In a typical terminal environment, the klystron is housed in a protective equipment cabinet, access to the tuning elements of which is accomplished by way of a panel door. When tuning the klystron, the terminal operator rotates a roller chart to view the number settings to which the slug tuning knobs must be set, unlocks the knobs from their current positions, and then proceeds to tune the klystron, adjusting the knobs in a prescribed sequence and in accordance with the strict number settings of the tuning chart. If a setting is exceeded, even only slightly, the tuning adjustment must be backed off considerably and the procedure reinitiated which eliminates mechanical backlash. It may be appreciated, therefore, that errors in operator accuracy involving conventional mechanical adjustment mechanisms can add excessive tolerances to an already critical procedure. In fact, it has been found the amplitude response of a klystron tuned by two different operators under the same conditions will seldom be the same for both operators.